The present invention relates to an optical pickup sending device for freely moving back and forth an optical pickup within an information recording/reproducing apparatus such as a disc player so as to read information from an information recording medium such as an optical disc.
There have been known several types of conventional pickup sending devices such as those disclosed in Japanese Utility Model Unexamined Publication No. 5-61861 and Japanese Patent Unexamined Publication No. 6-68619.
FIG. 6 is used to schematically indicate the structure of a conventional pickup sending device disclosed in Japanese Utility Model Unexamined Publication No. 5-61861. As shown in FIG. 6, the sending device comprises a pair of guide shafts 2 and 3 for slidably supporting an optical pickup body 1, a screwed shaft 4, a rack member 6 supported by two arm members 5 extending from the pickup body 1. The teeth 6a of the rack member 6 are engaged with the screwed shaft 4. When the screwed shaft 4 is rotated, a relative positional relationship between the teeth 6a and the screw shaft 4 will he changed, so as to cause the pickup body 1 to freely move back and fourth along the guide shafts 2 and 3, i.e., in a radial direction of an optical disc such as a CD (Compact Disc) mounted on a turntable (not shown).
With the pickup sending device shown in FIG. 6, although the rack member 6 is elastically urged by the screw shaft 4 through a least spring 6b provided in parallel with the arm members 5, since the teeth 6a of the rack member 6 are simply engaged with a part of the circumferential surface of the screwed shaft 4, an engagement between the teeth 6a of the rack member 6 and the screw shaft 4 is apt to collapse even due to a small vibration. As a result, it is difficult for the optical pickup 1 to read information from the optical disc in a correct manner and hence there will be some defects in the obtained information read by the optical pickup 1.
FIG. 7 is used to schematically indicate the structure of another conventional pickup sending device disclosed in Japanese Patent Unexamined Publication No. 6-68619. As shown in FIG. 7, the sending device comprises two guide shafts 8 and 9 for slidably supporting an optical pickup body 7 in a manner such that the pickup body 7 can be freely moved back and forth in the radio direction of an optical disc. A support member 10 is provided on the pickup body 7. The support member 10 has an engaging pin 12 provided at a front end thereof which is capable of engaging with a screw portion 11 formed integrally with the guide shaft 8. When the guide shaft 8 is rotated, a relative positional relationship between the engaging pin 12 and screw portion 11 will be changed, so as to cause the optical pickup body 7 to freely move back and fourth along the guide shafts 8 and 9.
With the pickup sending device shown in FIG. 7, since only the front end of the engaging pin 12 is engaged with the screw portion 11 of the shaft 8, an engagement between such two members 8 is apt to collapse even due to a small vibration. As a result, it is difficult for the optical pickup 7 to read information from the optical disc in a correct manner and hence there will be some defects in the obtained information read by the pickup 7.
In order to solve the problems existing in the above conventional devices shown in FIGS. 6 and 7, there has been suggested an improved structure shown in FIG. 8. Referring to FIG. 8, a half-nut 14 engaged with a screwed shaft 13, is integrally formed with a holding member 16 extending outwardly from the pickup main body 15. The inner diameter of the half-nut 14 is made almost the same as that of the screwed shaft 13, so that it is sure to prevent the half-nut 14 from getting off the screwed shaft 13.
However, if there is a relative deviation between a pair of guide shafts 17, 18 on one hand and the screwed shaft 13 on the other, an undesired gouging force will happen since it is difficult to absorb a dislocation caused by the above deviation between the screwed shaft 13 and the half-nut 14. As a result, there will he an unduly increased load on a driving motor (not shown) for driving the screwed shaft 13, hence undesirably causing an increase in the starting voltage of the driving motor.
It is an object of the present invention to provide an improved optical pickup sending device capable of solving the above-mentioned problems peculiar to the above-discussed prior arts.
According to the present invention, there is provided an optical pickup sending device, comprising: an optical pickup for reading information from an information recording medium; a rack member provided in connection with the optical pickup; and a screwed shaft engaged with the rack member for sending the optical pickup along the screwed shaft. In particular, the rack member is formed with a plurality of curved teeth each having a radius of curvature larger than that of the screwed shaft.
In one aspect of the present invention, the rack member is integrally formed with a holder so as to be supported thereby, said holder is engaged in a frame structure which is integrally formed with an arm member extending from he optical pickup and facing towards the screwed shaft.
In another aspect of the present invention, a coil spring is attached onto the holder in a manner such that the rack member is elastically urged against the screwed shaft.
The above objects and features of the present invention will become better understood from the following description with reference to the accompanying drawings.